package test01;

import java.util.LinkedList;
import java.util.Queue;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode root = new TreeNode(' ');
        root.left = new TreeNode(' ');
        root.right = new TreeNode(' ');
        return root;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root != null) {
            System.out.print(root.val + " ");
            preOrder(root.left);
            preOrder(root.right);
        }
        System.out.println();
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root != null) {
            inOrder(root.left);
            System.out.print(root.val + " ");
            inOrder(root.right);
        }
        System.out.println();
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root != null) {
            preOrder(root.left);
            preOrder(root.right);
            System.out.print(root.val + " ");
        }
        System.out.println();
    }

    public static int nodeSize = 0;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if(root == null) {
            return;
        }
        nodeSize++;
        size(root.left);
        size(root.right);

    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        return 1 + size2(root.left) + size2(root.right);
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if (root == null) {
            return;
        }
        if(root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if(root.left == null && root.right == null) {
            leafSize = 1;
            return leafSize;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if(root ==null){
            return 0;
        }
        if(k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left, k - 1) + getKLevelNodeCount(root.left,k -1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if (root.left == null && root.right == null) {
            return 1;
        }
        return getHeight(root.left) + getHeight(root.right);

    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        if(find(root.left, val) != null){
            return find(root.left, val);
        }
        if(find(root.right, val) != null){
            return find(root.right, val);
        }
        return null;

    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        Queue<TreeNode> queue = new LinkedList<TreeNode>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode node = queue.poll();
            System.out.print(node.val + " ");
            if (node.left != null) {
                queue.offer(node.left);
            }
            if (node.right != null) {
                queue.offer(node.right);
            }
        }
        System.out.println();

    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if (root == null) {
            return true;
        }
        Queue <TreeNode> queue = new LinkedList<TreeNode>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode node = queue.poll();
            if(node != null){
                queue.offer(node.left);
                queue.offer(node.right);
            }else {
                break;
            }
        }
        while (!queue.isEmpty()) {
            TreeNode node = queue.peek();
            if(node != null){
                return false;
            }
            queue.poll();
        }

        return true;
    }
}